Fine-Needle Aspiration Biopsy Technique and Specimen Handling

Introduction

Fine-needle aspiration (FNA) is widely used for evaluating palpable superficial masses and cysts as well as deep-seated, nonpalpable radiologic abnormalities under image-guidance. The capabilities and limitations of FNA, specific to the evaluation of a specific organ or anatomic site, are discussed in other chapters in this book.

In 1930, Martin and Ellis published the first significant North American description of FNA methodology for palpable lesions.¹ In spite of the long history of FNA and its application to the care of patients, there is no best practice for performing an FNA, and rigorous comparisons of biopsy techniques are lacking. Although the most common techniques for performing an FNA of a palpable mass are applicable to all superficial sites, there are nuances in method—some idiosyncratic—that depend on geographic or institutional custom and/or previous training and experience. Even for individual pathologists, details learned in training are often modified in practice by factors such as height, handedness, hand size, and finger strength.

Hands-on practical training in FNA technique is critical to developing the hand-eye coordination required. In comparison with physicians who had no formal training in FNA technique, those who received such training obtained diagnostic samples more frequently.² The best way to become proficient is to perform procedures under the direct supervision of someone who is proficient and provides feedback. Good training is important, but continued performance of procedures is necessary to maintain competence.

Materials and Supplies

All the equipment needed to perform an FNA (Table 8.1) is small and lightweight enough to be hand-carried in one container (Fig. 8.1A and B). This portability allows FNAs to be performed on demand and in virtually any setting. The equipment occupies only a small area of counter space when arranged for specimen preparation (Fig. 8.1C).

TABLE 8.1

FINE-NEEDLE ASPIRATION EQUIPMENT LIST

Figure 8.1 FNA equipment.
The syringe holder (A) and other items (B) are small enough to fit into a basket. They can be quickly assembled on a small amount of counter space (C). (B and C courtesy Sara Monaco, MD, University of Pittsburgh Medical Center, Shadyside Hospital.)

Procedure for Performing a Fine-Needle Aspiration of a Palpable Mass

The essential steps involved in performing an FNA of a palpable mass are demonstrated in the video that accompanies this chapter. Standard safety precautions must be observed during the biopsy procedure and in handling the harvested specimen.

Steps for a successful FNA

1. Determine if the FNA is warranted,

2. Consent the patient for the procedure.

3. Position the patient and immobilize the lesion.

4. Sample the targeted lesion adequately.

5. Prepare the sample for evaluation, including appropriate allocation of material for ancillary studies as necessary.

6. Provide post-procedure instructions to the patient.

Readying the Equipment

The biopsy apparatus is assembled by loading a syringe onto the syringe holder and attaching a needle. Needles 22 gauge or smaller are considered “fine.”³ Commonly, 23 and 25 gauge needles measuring 1.0 to 1.5 inches long are used for palpable lesions. Larger-gauge needles (19 to 22 gauge) are used for aspirating abdominal fat to test for amyloid deposition.^4–8 The shortest needle that reaches the furthest area of the lesion from the skin should be chosen. Shorter needles (less than 1.0 inch long) are sufficient for small nodules close to the skin surface. Needles vary in design; those with beveled tips are preferred, but FNA does not require a specific needle type to be successful. Once set up, the needle cap is loosened, and the equipment placed conveniently. If local anesthesia is to be given, it should be prepared at this time.

Because the sample must be prepared immediately before it dries/clots, several clean glass slides should be prelabeled with at least two patient identifiers (e.g., name, date of birth, medical record number), and alcohol slide fixative and a container filled with liquid transport medium should be at hand. These will be used to make smears, rinse the needle, and allocate material for special studies if necessary.

Positioning the Patient and Immobilizing the Lesion

The patient is positioned so that he or she is comfortable and the lesion can be palpated and immobilized. The patient should lie on their back when feasible; this is a safe position if there is a vasovagal response. Pillows, rolled towels, and foam shapes can be used for support. Changing the patient’s body position can dramatically affect the accessibility of the lesion. Breast masses, for example, are often best appreciated with the patient’s arm raised above the head. Neck nodules easily palpated in the sitting position may seem to disappear when the patient lies back. Becoming ambidextrous at FNA allows more flexibility in how the patient is positioned.

If the mass is beneath a band of skeletal muscle like the sternocleidomastoid, position the patient such that the muscle is relaxed, and move the muscle aside. In addition to being painful, passing a needle through skeletal muscle clogs the needle with skeletal muscle.

The exact methodology for stabilizing and immobilizing the mass varies by the site, the size of the mass, and the characteristics of the operator’s hands.

Once the method of immobilization and the needle trajectory have been determined, the skin is cleaned with an alcohol swab and local anesthesia injected (if desired). Buffered lidocaine solution tends to be less painful than unbuffered.⁹ Local anesthetic is advisable if the mass is tender to palpation or if the procedure involves a sensitive site like the nipple/areola. It is best not to inject so much local anesthetic that excessive skin swelling obscures the mass. This is particularly true with smaller nodules. The local anesthetic agent requires a few minutes to take effect.

Sampling the Lesion

Once the mass is fixed with the nonaspirating hand, the skin is cleaned with an alcohol swab at the planned needle entry site (see Video 8-1 found on expertconsult.com). The loosened needle cap is removed and the aspirating hand stabilized by resting the syringe barrel against the thumb or forefinger of the nonaspirating hand. This guards against any physiologic hand tremor and ensures precise needle placement but is not needed after insertion of the needle. The needle is inserted into the lesion, and the syringe plunger pulled back to generate several cubic centimeters of vacuum. The vacuum is maintained until the needle is removed from the patient. With a straight wrist, the needle is moved back and forth quickly and repeatedly in a sawing motion (“excursions”) for a dwell time no longer than 15 to 20 seconds (approximately 40 to 60 excursions) along the original needle trajectory, alternately advancing into the mass and withdrawing to a superficial location without exiting the patient. Slower needle action will yield less material. A shorter dwell time (2 to 5 seconds) is recommended for vascular lesions like thyroid nodules.¹⁰ Some practitioners also rotate the hand in a clockwise or counterclockwise fashion while it is moved within the lesion to achieve a “coring” effect, but this is not necessary. Each time the needle advances into the lesion, its cutting tip dislodges small tissue fragments; this cutting action is essential for a successful FNA. Negative pressure alone without needle movement will not procure enough tissue for diagnosis in solid lesions.¹ The vacuum in the syringe helps conduct the tissue fragments into the needle shaft and hub. A slight acceleration of the needle as it advances into the mass enhances the cutting action of the needle tip. Keeping the needle tip within the mass avoids diluting the specimen with adjacent nonlesional tissue. Material can be seen accumulating in the needle hub, although absence of visible material does not signify an inadequate sample. If blood is rapidly entering the hub, withdraw the needle immediately, especially in a vascular site like the thyroid gland.